/**
 * The MD5 class is used to compute an MD5 message digest over a given buffer of
 * bytes. It is an implementation of the RSA Data Security Inc MD5 algorithim as
 * described in internet RFC 1321.
 * 
 * @author Chuck McManis
 * @author Benjamin Renaud
 * @author Andreas Sterbenz
 */
public final class MD5 {

	// state of this object
	private final int[] state;
	// temporary buffer, used by implCompress()
	private final int[] x;

	// rotation constants
	private static final int S11 = 7;
	private static final int S12 = 12;
	private static final int S13 = 17;
	private static final int S14 = 22;
	private static final int S21 = 5;
	private static final int S22 = 9;
	private static final int S23 = 14;
	private static final int S24 = 20;
	private static final int S31 = 4;
	private static final int S32 = 11;
	private static final int S33 = 16;
	private static final int S34 = 23;
	private static final int S41 = 6;
	private static final int S42 = 10;
	private static final int S43 = 15;
	private static final int S44 = 21;

	// Standard constructor, creates a new MD5 instance.
	public MD5() {
		state = new int[4];
		x = new int[16];
		implReset();
	}

	// Cloning constructor
	private MD5(MD5 base) {
		this.state = base.state.clone();
		this.x = new int[16];
	}

	// clone this object
	public Object clone() {
		return new MD5(this);
	}

	/**
	 * Reset the state of this object.
	 */
	void implReset() {
		// Load magic initialization constants.
		state[0] = 0x67452301;
		state[1] = 0xefcdab89;
		state[2] = 0x98badcfe;
		state[3] = 0x10325476;
	}

	/**
	 * Perform the final computations, any buffered bytes are added to the
	 * digest, the count is added to the digest, and the resulting digest is
	 * stored.
	 */
	/*void implDigest(byte[] out, int ofs) {
		long bitsProcessed = bytesProcessed << 3;

		int index = (int) bytesProcessed & 0x3f;
		int padLen = (index < 56) ? (56 - index) : (120 - index);
		engineUpdate(padding, 0, padLen);

		i2bLittle4((int) bitsProcessed, buffer, 56);
		i2bLittle4((int) (bitsProcessed >>> 32), buffer, 60);
		implCompress(buffer, 0);

		i2bLittle(state, 0, out, ofs, 16);
	}
*/
	/* **********************************************************
	 * The MD5 Functions. The results of this implementation were checked
	 * against the RSADSI version.
	 * **********************************************************
	 */

	private static int FF(int a, int b, int c, int d, int x, int s, int ac) {
		a += ((b & c) | ((~b) & d)) + x + ac;
		return ((a << s) | (a >>> (32 - s))) + b;
	}

	private static int GG(int a, int b, int c, int d, int x, int s, int ac) {
		a += ((b & d) | (c & (~d))) + x + ac;
		return ((a << s) | (a >>> (32 - s))) + b;
	}

	private static int HH(int a, int b, int c, int d, int x, int s, int ac) {
		a += ((b ^ c) ^ d) + x + ac;
		return ((a << s) | (a >>> (32 - s))) + b;
	}

	private static int II(int a, int b, int c, int d, int x, int s, int ac) {
		a += (c ^ (b | (~d))) + x + ac;
		return ((a << s) | (a >>> (32 - s))) + b;
	}

	/**
	 * This is where the functions come together as the generic MD5
	 * transformation operation. It consumes sixteen bytes from the buffer,
	 * beginning at the specified offset.
	 */
	void implCompress(byte[] buf, int ofs) {
		ByteArrayAccess.b2iLittle64(buf, ofs, x);

		int a = state[0];
		int b = state[1];
		int c = state[2];
		int d = state[3];

		/* Round 1 */
		a = FF(a, b, c, d, x[0], S11, 0xd76aa478); /* 1 */
		d = FF(d, a, b, c, x[1], S12, 0xe8c7b756); /* 2 */
		c = FF(c, d, a, b, x[2], S13, 0x242070db); /* 3 */
		b = FF(b, c, d, a, x[3], S14, 0xc1bdceee); /* 4 */
		a = FF(a, b, c, d, x[4], S11, 0xf57c0faf); /* 5 */
		d = FF(d, a, b, c, x[5], S12, 0x4787c62a); /* 6 */
		c = FF(c, d, a, b, x[6], S13, 0xa8304613); /* 7 */
		b = FF(b, c, d, a, x[7], S14, 0xfd469501); /* 8 */
		a = FF(a, b, c, d, x[8], S11, 0x698098d8); /* 9 */
		d = FF(d, a, b, c, x[9], S12, 0x8b44f7af); /* 10 */
		c = FF(c, d, a, b, x[10], S13, 0xffff5bb1); /* 11 */
		b = FF(b, c, d, a, x[11], S14, 0x895cd7be); /* 12 */
		a = FF(a, b, c, d, x[12], S11, 0x6b901122); /* 13 */
		d = FF(d, a, b, c, x[13], S12, 0xfd987193); /* 14 */
		c = FF(c, d, a, b, x[14], S13, 0xa679438e); /* 15 */
		b = FF(b, c, d, a, x[15], S14, 0x49b40821); /* 16 */

		/* Round 2 */
		a = GG(a, b, c, d, x[1], S21, 0xf61e2562); /* 17 */
		d = GG(d, a, b, c, x[6], S22, 0xc040b340); /* 18 */
		c = GG(c, d, a, b, x[11], S23, 0x265e5a51); /* 19 */
		b = GG(b, c, d, a, x[0], S24, 0xe9b6c7aa); /* 20 */
		a = GG(a, b, c, d, x[5], S21, 0xd62f105d); /* 21 */
		d = GG(d, a, b, c, x[10], S22, 0x2441453); /* 22 */
		c = GG(c, d, a, b, x[15], S23, 0xd8a1e681); /* 23 */
		b = GG(b, c, d, a, x[4], S24, 0xe7d3fbc8); /* 24 */
		a = GG(a, b, c, d, x[9], S21, 0x21e1cde6); /* 25 */
		d = GG(d, a, b, c, x[14], S22, 0xc33707d6); /* 26 */
		c = GG(c, d, a, b, x[3], S23, 0xf4d50d87); /* 27 */
		b = GG(b, c, d, a, x[8], S24, 0x455a14ed); /* 28 */
		a = GG(a, b, c, d, x[13], S21, 0xa9e3e905); /* 29 */
		d = GG(d, a, b, c, x[2], S22, 0xfcefa3f8); /* 30 */
		c = GG(c, d, a, b, x[7], S23, 0x676f02d9); /* 31 */
		b = GG(b, c, d, a, x[12], S24, 0x8d2a4c8a); /* 32 */

		/* Round 3 */
		a = HH(a, b, c, d, x[5], S31, 0xfffa3942); /* 33 */
		d = HH(d, a, b, c, x[8], S32, 0x8771f681); /* 34 */
		c = HH(c, d, a, b, x[11], S33, 0x6d9d6122); /* 35 */
		b = HH(b, c, d, a, x[14], S34, 0xfde5380c); /* 36 */
		a = HH(a, b, c, d, x[1], S31, 0xa4beea44); /* 37 */
		d = HH(d, a, b, c, x[4], S32, 0x4bdecfa9); /* 38 */
		c = HH(c, d, a, b, x[7], S33, 0xf6bb4b60); /* 39 */
		b = HH(b, c, d, a, x[10], S34, 0xbebfbc70); /* 40 */
		a = HH(a, b, c, d, x[13], S31, 0x289b7ec6); /* 41 */
		d = HH(d, a, b, c, x[0], S32, 0xeaa127fa); /* 42 */
		c = HH(c, d, a, b, x[3], S33, 0xd4ef3085); /* 43 */
		b = HH(b, c, d, a, x[6], S34, 0x4881d05); /* 44 */
		a = HH(a, b, c, d, x[9], S31, 0xd9d4d039); /* 45 */
		d = HH(d, a, b, c, x[12], S32, 0xe6db99e5); /* 46 */
		c = HH(c, d, a, b, x[15], S33, 0x1fa27cf8); /* 47 */
		b = HH(b, c, d, a, x[2], S34, 0xc4ac5665); /* 48 */

		/* Round 4 */
		a = II(a, b, c, d, x[0], S41, 0xf4292244); /* 49 */
		d = II(d, a, b, c, x[7], S42, 0x432aff97); /* 50 */
		c = II(c, d, a, b, x[14], S43, 0xab9423a7); /* 51 */
		b = II(b, c, d, a, x[5], S44, 0xfc93a039); /* 52 */
		a = II(a, b, c, d, x[12], S41, 0x655b59c3); /* 53 */
		d = II(d, a, b, c, x[3], S42, 0x8f0ccc92); /* 54 */
		c = II(c, d, a, b, x[10], S43, 0xffeff47d); /* 55 */
		b = II(b, c, d, a, x[1], S44, 0x85845dd1); /* 56 */
		a = II(a, b, c, d, x[8], S41, 0x6fa87e4f); /* 57 */
		d = II(d, a, b, c, x[15], S42, 0xfe2ce6e0); /* 58 */
		c = II(c, d, a, b, x[6], S43, 0xa3014314); /* 59 */
		b = II(b, c, d, a, x[13], S44, 0x4e0811a1); /* 60 */
		a = II(a, b, c, d, x[4], S41, 0xf7537e82); /* 61 */
		d = II(d, a, b, c, x[11], S42, 0xbd3af235); /* 62 */
		c = II(c, d, a, b, x[2], S43, 0x2ad7d2bb); /* 63 */
		b = II(b, c, d, a, x[9], S44, 0xeb86d391); /* 64 */

		state[0] += a;
		state[1] += b;
		state[2] += c;
		state[3] += d;
	}

}
